Network channel access protocol—slot scheduling

ABSTRACT

Network channel access protocol is disclosed. More particularly, a distributed, locally determined, channel access protocol that adapts to load, avoids interference and controls access by a group of nodes to a set of shared channels is disclosed. Shared channel space is divided into a number of communication slots that are repeated at a predetermined interval. Permission to use a slot to communicate between any two nodes is dynamically adjusted by the channel access protocol, which locally: (i) estimates load to neighboring nodes; (ii) allocates or deallocates slot usage to adapt to load and avoid interference; and (iii) asserts and advertises slot usage within an interference area about itself.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/122,583, filed Apr. 15, 2002, now U.S. Pat. No. 7,113,519 whichclaims benefit of U.S. provisional patent application Ser. No.60/284,678, filed Apr. 18, 2001. Each of the aforementioned relatedpatent applications is herein incorporated by reference.

FIELD OF THE INVENTION

The invention relates generally to networks, and more particularly tonetwork protocols.

BACKGROUND OF THE INVENTION

Consumer appetite for access to information continues to grow along withgrowth of the Internet. Corresponding to such growth, new information isadded to the Internet constantly. With respect to multimedia content inparticular, much of this information comes at a significant cost inbandwidth.

Telephone dial-up service is being replaced with broader bandwidthsystems such as satellite, digital subscriber line (DSL), and cablemodem. Unfortunately, these systems are not presently available to asignificant portion of the population. Moreover, acquisition andinstallation costs associated with these systems make them lessappealing.

Accordingly, wireless connectivity is on the rise. Wireless systems maybe deployed more rapidly with less cost than their wired counterparts.Systems using cellular phone technologies are directed at providingmobile wireless Internet connectivity. Unfortunately, such systems arebandwidth limited.

Alternatives to cellular telephone technologies are cellulararchitectures providing high speed, data only services. An example isMulti-channel, Multi-point Distribution Service (MMDS) being provided bySprint. Benefits of wireless systems for delivering high-speed servicesinclude rapid deployment without overhead associated with installationof local wired distribution networks. Unfortunately, MMDS relies uponlong range transmissions and a sophisticated customer premiseinstallation.

What is needed is a fixed wireless solution with bandwidth comparable toDSL and cable modem technologies that is less complex to install andless costly. A mesh architecture and protocol serves these needs. InU.S. Pat. No. 5,682,3802 to Shepard, a fixed wireless network isdisclosed. In Shepard, the wireless network is based on a decentralizedpacket-radio concept using spread-spectrum technology for transmittingand receiving. Each station calculates a fixed pseudo-random schedule oftransmit and receive opportunities for communication and listens for thesame type of broadcast by other stations. Each station's schedule is intheory unique owing to its random or pseudo-random generation, so openspots in schedules may be found for communication opportunities bycomparing such randomly or pseudo-randomly generated schedules. Onlyimmediate neighbors for which a station will be in communication aremade aware of such schedules. Accordingly, Shepard does not providecoordination of use of channel space and has limited ability to adjustfor significant changes in traffic or load.

Therefore, it would be desirable to provide increased coordination ofchannel space use to mitigate against interference with other nodes andto adjust for significant changes in load. Moreover, it would bedesirable to locally coordinate such channel space use and providedynamic allocation of channel space.

SUMMARY OF THE INVENTION

An aspect of the present invention is a method for communication slotallocation and assertion for a planned transmission. More particularly,a node is provided, and an array of communication slots is obtained. Atleast one available communication slot within the array is located andallocated. It is determined if the at least one communication slot wasmade available by priority override. If the at least one communicationslot was made available by priority override, a prior allocation of theat least one communication slot is canceled and neighboring nodes of thenode are informed of the cancellation of the prior allocation. Usage ofthe at least one communication slot is asserted, and the neighboringnodes are informed of assertion of the at least one communication slot.It is determined whether the at least one communication slot isconfigured to receive or transmit. If the at least one communicationslot is configured to receive, use of the at least one communicationslot is scheduled.

Another aspect of the present invention is a method for slot allocationacknowledgement by a node. Slot allocation information is provided. Itis determined if the slot allocation information has been superseded,and if the slot allocation information has not been superseded, it isdetermined whether the slot allocation information pertains to the node.If the slot allocation information pertains to the node, a modeassociated with the slot allocation information is determined. If themode condition is transmit or receive, conflicts and interference arechecked using the slot allocation information. If the slot allocationinformation is not conflicted and not precluded by interference, use ofa communication slot identified by the slot allocation information isscheduled. It is determined whether the mode condition of the slotallocation information involves activity within an interference area ofthe node, and if the activity is within the interference area, the slotallocation information is advertised to neighboring nodes of the node.

The above as well as additional aspects of the present invention willbecome apparent in the following detailed written description.

BRIEF DESCRIPTION OF THE DRAWINGS

The teachings of the present invention can be readily understood byconsidering the following detailed description in conjunction with theaccompanying drawings, in which:

FIG. 1 is a network diagram depicting an exemplary portion of a networkin accordance with an aspect of the present invention;

FIG. 2 is a diagram of a house having consumer premises equipment (CPE)including computers and a node in accordance with an aspect of thepresent invention;

FIG. 3 is a block diagram of an exemplary portion of a network accesspoint (NAP) or a node in accordance with an aspect of the presentinvention;

FIGS. 4A through 4D are exemplary tables of data records in accordancewith an aspect of the present invention;

FIG. 5A is a block diagram of communication flow in accordance with anaspect of the present invention;

FIG. 5B is a flow diagram of an exemplary communication load program inaccordance with an aspect of the present invention;

FIG. 6A is a flow diagram of an exemplary slot allocation program inaccordance with an aspect of the present invention;

FIG. 6B is an exemplary frequency versus time slot matrix afterprocessing in accordance with an aspect of the present invention;

FIG. 7 is a flow diagram of an exemplary self-conflicts program inaccordance with an aspect of the present invention;

FIG. 8 is a flow diagram of an exemplary transmitting node intranetworkinterference program in accordance with an aspect of the presentinvention;

FIG. 9 is a flow diagram of an exemplary receiving node intranetworkinterference program in accordance with an aspect of the presentinvention;

FIG. 10 is a flow diagram of an exemplary slot allocation and assertionprogram in accordance with an aspect of the present invention;

FIG. 11 is a flow diagram of an exemplary acknowledgement program inaccordance with an aspect of the present invention;

FIG. 12 is a flow diagram of an exemplary frame execution program inaccordance with an aspect of the present invention; and

FIG. 13 is a flow diagram of an exemplary network join protocol inaccordance with an aspect of the present invention.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures.

DETAILED DESCRIPTION

Mesh Architecture

FIG. 1 is a network diagram depicting an exemplary portion of a network100 in accordance with an aspect of the present invention. Network 100comprises network access concentrators (SNAPs) 103, network accesspoints (NAPs) 101 and network access nodes 102. Network 100 traffic maybe routed from a network access node 102 to a neighboring network accessnode 102. Such a neighboring network access node 102 may route suchtraffic to one of its neighboring network access nodes 102 and so onuntil a NAP 101 or a final destination network access node 102 isreached. Notably, nodes 102 may be in communication with one another butnot with any node 101 to form a private wireless network.

SNAPs 103 may be coupled to various backhauls 105, which backhauls 105may be coupled to network 106. Network 106 may be coupled to anoperations center (OC) 104. Backhauls 105 may form a part of network106. Network 106 may comprise a portion of the Internet, a privatenetwork, or the like. By private network, it is meant a network notconnected to the Internet.

NAPs 101 may be in communication with SNAPs 103 or network 106 viabackhaul communication links 107. It should be understood that backhaulsmay be wired or wireless. In particular, backhauls coupled to NAPs 101may have a wireless backhaul. In an embodiment, point-to-pointcommunication is used as between a SNAP 103 and a NAP 101 in theUnlicensed National Information Infrastructure (UNII) band. Though, atlocations where wired connectivity is available, wired connectivity maybe used.

Network access nodes 102 are in wireless communication with at least oneNAP 101 or node 102. It should be understood that nodes 102 or NAPs 101may be configured for any of or some combination of broadcasting,point-to-point communication, and multicasting. By broadcasting, it ismeant transmitting without singling out any particular target recipientamong a potential audience of one or more recipients. By point-to-pointcommunication, it is meant transmitting with singling out a particulartarget recipient among a potential audience of one or more recipients.By multicasting, it is meant transmitting with singling out a pluralityof particular target recipients among a potential audience ofrecipients. For purposes of clarity, communication between nodes 102,between NAPs 101, or between a NAP 101 and a node 102, described belowis done in terms of point-to-point communication.

In one embodiment, this is done using radio communication in the UNIIband. However, other known bands may be used. Nodes 102 form, at leastin part, a Wide Area Network (WAN) using in part wireless interlinks108. More particularly, IEEE 802.11a physical and link layer standardsmay be employed for communication in a range of 9 to 54 megabits persecond (Mbits/s).

Communication slots as described herein are time slots with associatedfrequencies. However, one of ordinary skill in the art will understandthat other types of communication spaces may be used, including withoutlimitation codes, channels, and the like. Referring to FIG. 1, NAPs 101and nodes 102 communicate with one another and with each other bysending and receiving information during short time slots referenced tothe beginning of a frame. Each frame is approximately a same length oftime. By way of example and not limitation, each frame may beapproximately one second long, approximately beginning and ending oneach second. Notably, one or more time slots may exist within a frame.By way of example and not limitation, if a time slot has a length ofapproximately one millisecond, then approximately 1000 time slots may beavailable within a frame. Moreover, a frame may be divided intosubframes, as is known. For example, a 1 second frame may be dividedinto five 200 one-millisecond subframes, each of which contains 200 msslots.

Each node 102 and NAP 101 operates to a same time reference as eachother node and NAP in network 100, whether such time reference is a truetime or an arbitrary synch time. A reference time may be obtained bysatellite using GPS 310 of FIG. 3. Alternatively, a frame referencesignal may be transmitted between nodes at the beginning of a frameusing a special purpose time slot. By way of example and not limitation,such a special purpose time slot may be approximately 200 microsecondsin duration for transmission of approximately a one-microsecond pulse.

Nodes 102 may be located on roof-tops, for example as on a building 200illustratively shown in FIG. 2, in windows, in attics, on a pole, on atelephone pole, and the like. In FIG. 2, building 200 may house any of avariety of devices such as computers, printers, set-top boxes, PDAs, andlike devices, namely Customer Premises Equipment (CPE), having networkconnectivity capability, including without limitation connectivity tothe Internet. For purposes of illustration, computer 202 is shown wiredto node 102, and notebook computer 201 and PDA 204 are shown usingwireless connectivity such as a wireless local area network (WLAN). Byway of example, node 102 may comprise a 2.4 GHz PCMCIA LAN “card” forthe WLAN portion and a 100baseT or 10baseT Ethernet “card” for the wiredconnectivity portion. By “card,” it is meant to include integratedcircuit chip or a printed circuit board comprising one or moreintegrated circuit chips. Such wired and wireless interfaces form aportion of interface 309, as illustratively shown in FIG. 3.

Referring to FIG. 3, there is shown a block diagram of exemplaryportions of NAP 101 and node 102 in accordance with aspects of thepresent invention. A NAP 101 comprises a node 102 operatively coupled toa backhaul communication device 308. NAPs 101 and nodes 102 arehereinafter collectively referred to as nodes 300.

Multi-sectored antenna 301 comprises sectors 301-0 to 301-7. Though aneight-sectored antenna 301 is illustratively described herein, antenna301 may comprise fewer or more sectors than eight, namely, 1 to qsectors for q an integer. Though a sectored antenna is described, otherantenna configurations may be used, including but not limited to anomni-directional antenna, a collection of individually pointeddirectional antennas, a combination of a sectored antenna and anomni-directional antenna, and the like.

Antenna 301 is coupled to multi-pole switch 302 for selectivelyaccessing a sector of sectors 301-0 through 301-7. Sectors 301-0 through301-7 may be arranged in banks, such that multi-pole switch 302 may beused to select such a bank. Switch 302 is coupled to transceiver(hereinafter “radio”) 304. In an embodiment, radio 304 may beimplemented using a 5.8 GHz UNII band radio. However, other radios withother frequencies may be used.

Radio 304 is coupled to radio controller 305. In an embodiment, radiocontroller 305 may be implemented using a field programmable gate array.Radio controller 305 is coupled to a single board computer (SBC) 306.SBC 306 comprise a processor and memory 307 capable of storing a datastructure 312. SBC 306 is configured for routing traffic, and in thiscontext may be considered a router.

SBC 306 is coupled to interface 309. Interface 309 may comprise a WLANcard, an Ethernet card, or the like as mentioned above. Backhaulcommunication device 308 may be coupled to SBC 306 via interface 309 oroptionally directly coupled to SBC 306. Backhaul communication device308 depends on the type of backhaul used, as mentioned elsewhere hereinsuch a backhaul may be wired or wireless.

Optionally, a Global Positioning System (GPS) card 310 and antenna 311may be used. GPS antenna 311 is coupled to GPS card 310. GPS card 310 iscoupled to radio controller 305 and SBC 306.

Each node 300 may have at least one neighboring node 300. By neighboringnodes, it is meant other nodes 300 with which a node 300 may be put indirect communication. By way of example, if A, B and C are nodes, and Amust communicate through B in order to communicate with C, then A and Bare neighbors, B and C are neighbors, and A and C are not neighbors.

Each node 300 maintains a database of information regarding nodes in itsvicinity. Such a database may be stored in memory 307 in a form of adata structure 312. This database may be shared among nodes 300 in aninterference area. By interference area, it is meant a region about anode in which communication to or from said node may be interfered withby another node. In other words, an interference area is an area about anode 300 in which such node's radio transmissions may be heard or maycause interference with another transmission. This area is convenientlyapproximated by a radius, r, about such a node 300. Radius, r, may beestimated using an RF propagation model and is dependent on frequencyband and transmit power among other factors, including but not limitedto terrain, vegetation, buildings, and the like.

Sharing information can occur by a node 300 transmitting over interlinks108 information to neighboring nodes 300, which may retransmit suchinformation to their neighboring nodes 300, and so on. Such a databasemay comprise information on node location, antenna direction, slotusage, control parameters, routing, among other types of information.Examples of data records are illustratively shown in FIGS. 4A through4D.

Information in FIGS. 4A through 4D is provided by way of example, andaccordingly other fields and field information types and values may beused. Each example data record comprises a “Field,” “Key,” “Type, ”“Units,” and “Bytes” column. “Field” indicates a type of information fora field. “Key” indicates a key field in a database. “Type” indicates aninformational type for describing field information, such as nodeidentification, integer, time, and floating point value. “Units”indicates units for such field information. “Bytes” indicate storagespace allocated for such field information.

A “Node” field identifies a node for which a respective data recordpertains. An “At” field designates a time at which a data record wascreated or modified. A “By” field indicates which node created ormodified such a data record. A “Sequence” field in each record indicatesan incremented record number and is for a repair protocol, in particularfor establishment of a database on a node to network 100.

Data record 401 of FIG. 4A is a locator record and comprises “Latitude”and “Longitude” fields, among other fields previously described herein.A “Latitude” field indicates a latitudinal position of a node for whichdata record 401 pertains, and a “Longitude” field indicates longitudinalposition for such a node. This information may be obtained from a GPSamong other sources of such information. Field “laccuracy” is accuracyin meters of a location estimate. In other words, a node is within somany meters of a specified latitude and longitude. Field “nantenna” is anumber of antenna sectors. Field “orientation” is a direction in whichan antenna sector, for example sector 0, is pointing. This value is indegrees relative to true north. With a fixed array of equally spacedantenna sectors, orientations of other sectors may be computed usingfields “nantenna” and “orientation”. Field “oaccuracy” is accuracy indegrees of an orientation estimate. Using information from data record401, antenna azimuth and beam width may be derived by node 300.

Data record 402 of FIG. 4B is a slot usage data record. Data record 402is updated to allocate or deallocate a communication slot. Any node 300shown in FIG. 3, in particular a transmitting node, may update datarecord 402. Updates to slot allocation records may be made intransmitting, tx, and receiving, rx, record pairs. Data record 402comprises “Function,” “Time Slot,” “Frequency, ” “Antenna,” “OtherNode,” and “Expiration Time” fields, among other fields previouslydescribed herein.

A “Function” field indicates a function for a communication slot, suchas not presently allocated (“none”), transmit, or receive.

A “Time Slot” field indicates a selected time slot t from 0 to m−1 of mtime slots for execution of a transmit or a receive function.

A “Frequency” field indicates a select frequency f from 0 to n−1 of nfrequencies for execution of a transmit or a receive function.

An “Antenna” field indicates a sector selected for execution of atransmit or a receive function.

An “Other Node” field identifies a target recipient node for a message.However, other node field could be a multicast or a broadcast indicator.

An “Expiration Time” field indicates an expiration time for allocationof a slot for a function. After expiration time has lapsed, nodes treatfunction for data record 402 as “none.” However, prior to lapsing,expiration time may be reset for additional communication slot usage.

A “Priority” field indicates a priority value for slot allocation. Ifall slots are allocated, priority may be given to one subscriber overanother based on a priority value. This priority value may be from 0 tosome integer p.

Data record 403 of FIG. 4C is a control parameter data record. Inaddition to Node, Priority, By, At and Sequence fields previouslydescribed, data record 403 comprises a “Max. Bandwidth” field whichindicates a maximum bandwidth limit allocated to a node identified insuch a data record.

Data record 404 of FIG. 4D is a routing cost data record. In addition toBy, At and Sequence fields previously described, data record 404comprises “Source Node”, “Destination Node”, “Cost” and “Dynamic”fields. A “Source Node” field indicates a source node or a beginningpoint on a route. A “Destination Node” field indicates a targetdestination of such a route, namely, a final destination for such aroute. A “Dynamic” field indicates whether dynamic or static routing isto be used. A “hop” field indicates a route selected from one or moreknown routes for routing traffic from a source node to a destinationnode.

A “Cost” field indicates a determined cost for sending such a messagefrom a source node to a destination node. Such a cost may be staticallyor dynamically determined.

It should be understood that data records illustratively shown in FIGS.4A through 4D are not meant to include all possible data records. Otherdata records may include current and alternative routes, control andstatus information, distance and azimuth between each pair of nodes,among others. Furthermore, it should be understood that one or morefields illustratively shown may be omitted in implementing one or moreaspects of the present invention. Moreover, it should be understood thatnodes 300 each maintain a portion of a database for network 100, andthus a shared or distributed database among nodes is provided.Furthermore, it should be appreciated that network 100 may functionwithout centralized control.

It should be understood that a mesh architecture in accordance with anaspect of the present invention is herein disclosed. This architectureuses packet-based transmission of data. Each node 300 of FIG. 1 providesa router for communicating traffic. Accordingly, protocols are needed toimplement such a mesh architecture. For example, when a node 300determines to route traffic to a particular next hop, data packets beginaccumulating at that node for transmission to such a next hop. Asufficient number of communication slots need to be allocated to supporttransmission of such a load of data packets, and this is done locally ateach node 300 for distributed access control as disclosed in more detailbelow. Moreover, as network 100 is dynamic, allocation of slots ischecked and adjusted periodically by comparing to current estimates ofload, as disclosed below in more detail.

Transmission Load

Referring to FIG. 5A, there is shown a block diagram of transmissionload flow in accordance with an aspect of the present invention.Basically, three types of incoming transmissions are received at node300, namely transmissions where node 300 is an intended recipient ofinformation, as indicated by arrows 508; transmissions where node 300 isused to forward information, as indicated by arrows 503; andtransmissions where node 300 receives information for CPE 500 asindicated by arrows 504.

Information associated with arrows 504 may be sent to CPE 500 asindicated. Additionally, CPE 500 may provide information fortransmission to node 300, as indicated by arrows 505. Node 300 may haveto transmit overhead information, as indicated by arrows 506, or receiveoverhead information as indicated by arrows 508. Such overheadinformation may include information to maintain network 100 includingsharing of database information and the like. Notably, program 510 ofFIG. 5B measures incoming traffic to be relayed by node 300, asindicated by arrow 503, and outgoing traffic, either from CPE 500 oroverhead traffic, to be sent by node 300, as indicated by arrows 505 and506, as explained below. Though an example of measurement locations isprovided, other approaches to measuring traffic load may be used.

Referring to FIG. 5B, there is shown a flow diagram of an exemplarytransmission load program 510 in accordance with an aspect of thepresent invention. With continuing reference to FIG. 5B and renewedreference to FIGS. 3 and 5A, operation of program 510 is described.Program 510 provides estimates for communication slot needs of a node300 for communication to each neighboring node 300. Program 510 may beresident at each node 300, for example in memory 307.

Program 510 comprises program portions 520 and 521. Program portion 520is for estimating what a transmission output load (OL) may be in thenear future, approximately 1 to 30 seconds in the future. Programportion 521 is for determining a slot allocation based on such anestimated OL obtained from program portion 520.

Program 510 is initialized at step 511. This initialization begins acurrent estimation period. A subsequent estimation may follow at apredetermined time interval after the starting time for a currentestimation. Such a time interval may be in a range of approximately 0.1to 10 seconds after initiation of such a current estimation. Notably, itis assumed that nodes 300 of FIG. 3 have already joined network 100. Anetwork joining protocol is disclosed in more detail below herein.

At step 526, a neighboring node of a group of neighboring nodes isselected.

At step 512, incoming traffic or input load (IL) for such a neighboringnode selected at step 526 is determined. This determination may be madeby measuring load at selected locations. For example, as mentioned abovewith respect to FIG. 5A, IL may be provided by adding together incomingtraffic to node 300 to be forwarded to such a neighboring nodeidentified at step 511, outgoing traffic from CPE 500 to be sent to sucha neighboring node identified at step 511, and overhead traffic fromnode 300 to be sent to such a neighboring node identified at step 511.However, other combinations and types of loads may be used to provide anIL.

At step 513, IL determined at step 512 is compared against OL. If IL isless than or equal to OL, then at step 514, a new value for OL is setaccording to:OL=[t*(IL)+(1−t)(OL)],  (1)where t is an adjustable time constant in a range of 0.0 to 1.0. By wayof example and not limitation, t may be set equal to approximately 0.3.Higher values of t yield a more responsive estimate, while lower valuesprovide a smoother estimate.

If, however, IL is greater than OL, then at step 515, a new value for OLis set equal to a factor k times IL from step 512, namely:OL=k*IL,  (2)where k is generally somewhat greater than 1. Thus, the estimate of OLis highly responsive to large rises in IL, but decays exponentially whenIL falls off.

At step 516, a number of communication slots is estimated using OLobtained at step 514 or 515. This estimation is,Slots Required=OL/[(Slot Length)(Data Rate)].  (3)

Notably, an embodiment of equal slot lengths is described. However, itshould be understood that variable slot lengths may be used. Forexample, a slot length may be in a range of approximately a couplehundred microseconds to several milliseconds. In an embodiment describedherein, a 1 ms slot length is used.

At step 517, the number of communication slots computed at step 516 iscompared to a number of communication slots currently allocated forcommunicating with such a neighboring node. If the estimated number ofslots is less than the currently allocated number of slots, then at step518, the number of slots allocated is decreased. The number of slotsdeallocated may be done based on priority. For example, one or moreslots, starting from a lowest priority, may be deallocated. Moreover, ifa slot selected for deallocation is due to expire within a short period,for example approximately 0 to 20 seconds, it may not be necessary toexplicitly deallocate such a slot, as such a slot will be deallocatedautomatically by all affected nodes at such an expiration time.

If, however, the estimated number of slots at step 516 is greater than anumber of currently allocated slots for communication with such aneighboring node, then at step 519, slot allocation may be increased. Ifat step 519 there are not a sufficient number of free slots to beallocated, then currently allocated slot usage may be overridden basedon priority. Using priority to override a slot allocation is describedin more detail below.

If current slot allocation equals the estimated number of slots at step516, then no change in allocation is made, as indicated by progressionfrom step 517 to step 522.

At step 522, expiration time of allocated slots for such a neighbor ischecked. For each slot scheduled to expire soon, for example withinapproximately 0 to 20 seconds, slot expiration time is extended.

At step 524, a check for a next neighboring node 300 is made. If thereis another neighboring node 300, then program 510 continues at step 512.

If at step 524 no other neighboring node 300 is to be processed, then atstep 525, program 510 is paused until the above-mentioned predeterminedtime has lapsed. In other words, program 510 waits for a next estimationperiod to begin, upon which program 510 begins a subsequent iteration atstep 512 by measuring an IL value anew.

Slot Availability

As mentioned above with respect to step 519, additional slots areallocated to handle an estimated output load. FIG. 6A is a flow diagramof an exemplary slot allocation program 600 in accordance with an aspectof the present invention.

Step 519 of FIG. 5B may comprise or invoke program 600. Program 600 maybe employed either for a message destination or a receiving node, R, orfor a message originating or a transmitting node, T. For purposes ofclarity, program 600 is described for determination of slot allocationat a transmitting node T; however, it will be apparent to those of skillin the art of the present invention that program 600 may be used todetermine slot allocation at a receiving node, R. Program 600 may beresident in memory 307 of FIG. 3.

At step 601, override priority is set to the lowest priority. Thus, afirst attempt at slot allocation will not override any existingallocations as will become apparent.

At step 602, an m-by-n array for times and frequencies, respectively, iscreated and filled with zeros. Again, as mentioned above, communicationspace may be defined by parameters other than time and frequency.Moreover, by array, it is meant to include a table, a list, and thelike.

At step 603, one or more slot allocation already made at T areidentified as one or more “self-conflicts” respectively. At step 604,one or more slot allocations already made at R are identified by T asone or more “self-conflicts” respectively. Allocations at T or R, whichmight conflict with transmission from T to R, are termed“self-conflicts.” For multicasting, each R is checked forself-conflicts. Conflicts or interference internal to network 100 ofFIG. 1, not “self-conflicts,” are termed “intranetwork” conflicts orinterference, and all other conflicts or interference not“self-conflicts” or “intranetwork” interference are termed “external”conflicts or interference. Self-conflicts, intranetwork interference andexternal interference are operationally defined in more detail below.

At steps 603 and 604, respectively, time slots associated with“self-conflicts” are marked as unavailable by incrementing respectivelocations in the array of step 602, for example from zero to one, or oneto two, and so on. Moreover, a priority check may be done foravailability by priority override, as described below in more detail.

At step 605, each node 300 (shown in FIG. 3), other than T and R, ischecked to determine if it has a transmit slot allocation that mayinterfere with T transmitting to R or vice versa. Again, formulticasting there will be a plurality of receiving nodes R or viceversa. These conflicts are identified as “intranetwork” conflicts. Thesenodes 300 (shown in FIG. 3) are limited to nodes within an interferencearea. Slots associated with such intranetwork interference are marked asunavailable by incrementing respective locations in the array of step602. Moreover, a priority check may be done for availability by priorityoverride, as described below in more detail.

At step 606, each node 300 (shown in FIG. 3), other than T and R, ischecked to determine if it has a receive slot allocation that may beconflicted with by T transmitting to R. Again, for multicasting, therewill be a plurality of receiving nodes R. These nodes 300 (shown in FIG.3) are limited to nodes within an interference area. At step 606, timeslots associated with such intranetwork interference are marked asunavailable by incrementing respective locations in the array of step602. Moreover, a priority check may be done for availability by priorityoverride, as described below in more detail.

At step 607, time slots compromised by “external” conflicts areidentified. Such “external” interference may be due to other in-bandusers. Detection of such external interference is described below inmore detail. Such time slots associated with external conflicts areidentified, and accordingly respective locations in the array of step602 are incremented.

If there are one or more self-conflicts, intranetwork interference, and“external” interference, the array of step 602 comprises non-zeroentries associated with such conflicts and interference. If there are noconflicts for some of the communication slots, then the array of step602 will have zero entries for those slots indicating that they areavailable.

An example of a resultant array 620 is illustratively shown in FIG. 6Bfor frequency 699 versus time 698. Steps 602 through 607 compriseinterference and conflict identification portion 615 of program 600.Notably, the order of steps 603 through 607 is not binding and may bealtered.

At step 608, communication slots are selected and allocated from thoseslots remaining available. Any element in the array of step 602 thatremains a zero is available for use between T and R, or, in amulticasting embodiment, for use between T and Rs. Such selection may bedone in a pseudo-random manner. The number of communication slotsneeding to be allocated is determined by program 510 of FIG. 5B, asdescribed above. At step 609, the number of slots requested to beallocated in program 510 of FIG. 5B is decreased by the number of slotsallocated at step 608.

At step 610, a determination is made as to whether the number ofcommunication slots allocated at step 608 was sufficient. If asufficient number of communication slots have been allocated, thenprogram 600 ends at step 611. If however, a sufficient number ofcommunication slots have not been allocated, then step 610 proceeds tostep 612. In other words, there presently is an insufficient number oftime slots available to support an output load estimated in program 510of FIG. 5 without overriding one or more existing slot allocations.

If not enough slots were allocated at step 610, then at step 612override priority is incremented. At step 613, a check is made todetermine if override priority is greater than or equal to priority of anext slot allocation attempt to fulfill this ongoing allocation effort.If override priority is less than priority of a next slot allocationattempt, then program 600 begins anew at step 602.

If, however, override priority equals or is greater than priority of anext slot allocation attempt, then at step 611, program 600 ends.Accordingly, it should be understood that program 600 may end withhaving made only a partial allocation or no allocation at all. In otherwords, network 100 may be congested, in which case there may not beenough communication slots available for sending an estimated outputload.

Slot Availability and Self-Conflicts

In FIG. 7, there is shown a flow diagram of an exemplary self-conflictsprogram 700 in accordance with an aspect of the present invention. Withcontinuing reference to FIG. 7 and renewed reference to FIG. 6A, step603 may be replaced by steps 701 through 705.

At step 701, an initial time slot is obtained.

At step 702, T is checked to determine if it has been pre-allocated totransmit or receive during the time slot obtained from step 701, asapplicable. If T is not pre-allocated for transmitting or receivingduring such a time slot, then a check for a next time slot is made atstep 705. Thus, the array from step 602 is left unchanged for allfrequencies in this time slot.

If, however, T is pre-allocated for transmitting or receiving duringsuch a time slot, then this indicates a self-conflict. At step 703 apriority check is made. If override priority is greater than theexisting usage priority, then a check for a next time slot is made atstep 705. Thus, the array from step 602 is not incremented indicatingavailability of all frequencies in this time slot.

If, however, override priority is equal to or less than priority of theexisting usage priority, then this time slot and all frequencies in thistime slot are marked as unavailable at step 704 by incrementing thoselocations in the array of step 602.

At step 705, a determination is made as to whether there is at least onemore time slot to be checked for self-conflicts. If so, then at step 701another time slot is obtained. If, however, there is no other time slotleft to be checked for a self-conflict, then program 700 ends.

With continuing reference to FIGS. 6A and 7, T may be replaced with R insteps 701 through 705, and then step 604 may be replaced by steps 701through 705 checking for self-conflicts of R instead of T. Moreover,steps 701 through 705 may be done for each R in a multicastingembodiment.

Slot Availability and Intranetwork Interference

In FIG. 8, there is shown a flow diagram of an exemplary transmittingnode intranetwork interference program 800 in accordance with an aspectof the present invention. Step 605 of FIG. 6A may be replaced by steps801 through 809.

With continuing reference to FIG. 8 and renewed reference to FIG. 6A, atstep 801, a node, other than T or R, is selected. Such a node is termed“other node” to indicate it is a node other than T or R, or T or Rs in amulticasting embodiment. Such “other node” is within an interferencearea of T or R, or T or Rs in a multicasting embodiment. At step 802, atime slot is selected. At step 803, a determination is made as towhether such other node selected at step 801 is receiving during suchtime slot selected at step 802. If such other node is not receiving,then a check for another time slot is made at step 808. In other words,the array of step 602 will be unaltered with respect to such other nodeand such a time slot.

If, at step 803, such other node is pre-allocated to receive during sucha time slot selected at step 802, then at step 804 a determination ismade as to whether override priority is greater than such other node'susage priority. If override priority is greater, then a check foranother time slot is made at step 808. In other words, the array of step602 will be unaltered with respect to such other node and such a timeslot.

If, however, at step 804 such other node's usage priority is equal to orgreater than override priority, then at step 806 it is determinedwhether power from T's transmission, or more particularly an estimatedreceived power at such other node resulting from T's transmission, islikely to interfere with such other node's reception. Received power maybe estimated by knowledge of transmit and receive antenna patterns usingan RF propagation model such as Longley-Rice or Unified Ultra-HighFrequency (Unified UHF), and likely to interfere may be determined bycomparison of an expected received power at such other node caused by(i) transmission from T and (ii) transmission to such other node from anintended transmitter. Conventionally, when a ratio of intended powerdivided by interference power is less than a signal-to-interferenceratio (SIR) threshold, where SIR threshold is modulation dependent,interference is likely. Conventional values are approximately 20decibels. If interference is unlikely, then another time slot isselected at step 802. If interference is likely, then at step 807 suchtime slot and such other node's selected frequency is marked asunavailable by incrementing that location in the array of step 602.Notably, there is a difference between self-conflicts and intranetworkconflicts with respect to marking frequencies as unavailable.

At step 808, a determination is made as to whether there are more timeslots to check for such other node. If there is at least one other timeslot to check, then another time slot is selected at step 802.

If there is no other time slot to check for such other node, then atstep 809 a determination is made as to whether at least one other nodeis to be processed. If at least one other node is to be processed, thensuch other node is selected at step 801. If no other node is to beprocessed, then program 800 ends.

In FIG. 9, there is shown a flow diagram of an exemplary receiving nodeintranetwork interference program 900 in accordance with an aspect ofthe present invention. Step 606 of FIG. 6A may be replaced by steps 901through 909.

With continuing reference to FIG. 9 and renewed reference to FIG. 6A, atstep 901, a node, other than T or R, or T or Rs in a multicastingembodiment, is selected. Such other node is within an interference areaof T or R, or T or Rs in a multicasting embodiment. For purposes ofclarity, hereinafter R is used to mean R, as in point-to-pointcommunication, and Rs, as in point-to-multipoint communication. At step902, a time slot is selected. At step 903, a determination is made as towhether such other node selected at step 901 is pre-allocated totransmit during such time slot selected at step 902. If such other nodeis not transmitting, then another time slot is selected at step 902. Inother words, the array of step 602 will be unaltered with respect tosuch other node and such a time slot.

If at step 903, such other node is pre-allocated to transmit during sucha time slot selected at step 902, then at step 904 a determination ismade as to whether override priority is greater than planned usagepriority. If override priority is greater than planned usage priority,then a check for another time slot is made at step 908. In other words,the array of step 602 will be unaltered with respect to such other nodeand such a time slot.

If, however, at step 904 such other node's planned usage priority isequal to or greater than override priority, then at step 906 it isdetermined whether power from such other node's transmission, or moreparticularly an estimated received power from such other node'stransmission, is likely to interfere with R's reception. If interferenceis unlikely, then a check for another time slot is made at step 908. Ifinterference is likely as described above, then at step 907 such timeslot and such other node's selected frequency is marked as unavailableby incrementing that location in the array of step 602.

At step 908, a determination is made as to whether there is another timeslot to check for such other node. If there is at least one other timeslot to check, then another time slot is selected at step 902. If thereis no other time slot to check for such other node, then at step 909 adetermination is made as to whether at least one other node is to beprocessed. If at least one other node is to be processed, then suchother node is selected at step 901. If no other node is to be processed,then program 900 ends.

External Interference

With renewed reference to FIG. 6A, at step 607 a determination ofconflict by external interference is made. Nodes 300 (shown in FIG. 3)build a database comprising such external interference as detected inthe course of operation, as described in more detail below. Thisdatabase comprising discovered external interference is checked and ifit appears likely that one will transmit during a time slot, at afrequency, and with sufficient power to interfere with a scheduledtransmission from T to R, then such a time slot and frequency are markedas unavailable in the array.

Slot Allocation and Assertion

After completion of program 600 shown in FIG. 6A with respect toidentification of self-conflicts, intranetwork interference, andexternal interference, allocated communication slots are to be asserted.Referring to FIG. 10, there is shown a flow diagram of an exemplary slotallocation and assertion program 1000 in accordance with an aspect ofthe present invention.

With continuing reference to FIG. 10 and renewed reference to FIGS. 5Band 6A, at step 1001, slot allocation is determined by accessing anarray as processed by program 600. Available slots, as indicated in thearray of step 602 as amended, are pseudo-randomly selected in a numbersufficient to fulfill or partially fulfill that amount of communicationslots identified at step 519 of program 510. Thus, at step 519, program1000 may be called by program 510 for such allocation. With respect totime slot allocation, it should be understood that a time slot may haveone or more frequencies associated with it. Thus, while one or morefrequencies associated with a time slot are unavailable, one or moreother frequencies associated with such a time slot may be available,except that if a slot is chosen at a specific time and frequency, noother slot may be selected at that same time even if another frequencyis also available.

At step 1002, a slot allocated at step 1001 is accessed. At step 1003,it is determined whether such an allocated slot was made available bypriority override. For each such slot made available by priorityoverride, at step 1004, an asserting node cancels another's slotallocation and then may assert its own slot allocation. All neighboringnodes, whether one or more neighbors, of such a node canceling suchusage are informed of this cancellation at step 1005 using communicationbetween nodes.

If no priority override leading to cancellation of this slot allocationoccurred at step 1004, then such a node asserts its allocation withoutsuch cancellation at step 1006.

At step 1006, slot usage is asserted for such a communication slot forsuch a future use. At step 1007, all neighboring nodes, whether one ormore neighbors, of such a node making such slot allocation are informedof assertion of such a communication slot usage by communication betweennodes. By assertion, it is meant that an actual allocation is made in adatabase shared among nodes.

At step 1008, usage of an asserted slot allocation is determined, namelyto transmit or receive. If an asserted slot allocation is to have anasserting node receive data, then that allocation is scheduled at step1009 for execution in a current or one or more subsequent frames. If anasserted slot allocation is to have an asserting node transmit data,program 1000 looks for another slot at step 1010.

At step 1010, a check is made for another slot. If there is another slotto be allocated, then a next slot is allocated at step 1002. If there isno other slot to be allocated, then at step 1011 program 1000 ends.

Referring to FIG. 11, there is shown a flow diagram of an exemplaryacknowledgement program 1100 in accordance with an aspect of the presentinvention. It should be understood that program 1100 may be run at a Tor an R node or at a neighboring node of an asserter of a slotallocation.

At step 1101, a slot allocation transmission associated with informationsent at step 1007 of FIG. 10 is received at a neighboring node of anasserting node. At step 1102, a determination is made as to whether suchslot allocation transmission has been superseded by other informationalready received and stored at such neighboring node. Examples ofreasons for supersession include a delay in transmission owing to afault in network 100 (shown in FIG. 1), simultaneous assertion of a sameslot by differing nodes 300 (shown in FIG. 3), and the like. If suchslot allocation transmission has been superseded, then program 1100terminates at step 1114.

If such slot allocation information has not been superseded, then atstep 1102A slot allocation information is stored. Then at step 1103, adetermination is made as to whether such slot allocation pertains tothis node, namely, a node executing program 1110.

If such slot allocation does not pertain to this node, then program 1110proceeds to step 1108. At step 1108, a node determines whethertransmission associated with such slot allocation is within such node'sinterference area. If at step 1108 such transmission associated withsuch slot allocation is within such interference area, then at step 1109such node executing program 1100 advertises to all its neighboringnodes, whether one or more neighbors of this slot allocation received atstep 1101. If at step 1108 such transmission associated with such slotallocation is not within an interference area of such a node executingprogram 1100, then program 1100 terminates at step 1114.

If, however, at step 1103 this slot allocation pertains to such a noderunning program 1100, then at step 1104, a determination is made as towhat mode such a slot allocation indicates. If a no mode or nonecondition is indicated, for example if another node has canceled orrejected a slot allocation, then this slot allocation usage is canceledat step 1113 followed by a check at step 1108 as previously described.If at step 1104 it is determined that such a node is to transmit orreceive during such slot allocation, then a check for conflicts andinterference is made at step 1110. Step 1110 executes program 615 (shownin FIG. 6A) to determine if this slot allocation is acceptable. If suchslot allocation is acceptable, then at step 1105, a check is made as towhether mode is to transmit or receive for such a node. If the mode isreceive, the message is acknowledged at step 1106. Then, for eithermode, at step 1107 such slot allocation is scheduled for use followed bya check at step 1108 as previously described.

If, however, at step 1110 or 1105, it is determined that a slotallocation received at step 1101 is not acceptable, then at step 1111such slot allocation usage is canceled, and at step 1112 suchcancellation is advertised to all neighboring nodes, whether one or moreneighbors, of the node running program 1100. After which, program 1100terminates at step 1114.

Frame Execution

FIG. 12 is a flow diagram of a frame execution program 1200 inaccordance with an aspect of the present invention. In addition totransmitting and receiving messages, frame execution program 1200 isconfigured for operationally determining external interference inreal-time. Program 1200 may be resident in memory 307 of a node 300(shown in FIG. 3) and runs continuously, stepping through each time slotin a frame, or if all slots have been processed, then going through eachslot in a next frame, and so on.

At step 1202, program 1200 waits for a frame synchronization indicator.After receipt of a frame synchronization signal, at step 1203 a firstcommunication slot is selected and used at a node executing program1200.

At step 1204, it is determined which mode, transmit, receive, or none,is associated with such a selected slot at step 1203. If such a slot isallocated for transmitting, then at step 1205 information istransmitted, and at step 1206 a check is made for another slot in such aframe. If there is no other slot to access, then a next framesynchronization signal is awaited at step 1202. If there is another slotat step 1206, then at step 1203 another slot is selected and used.

If such a slot is not allocated for transmitting or receiving at step1204, then at step 1206 a check for another slot is made. If at step1204 it is determined that a slot is allocated for receiving, then atstep 1207 a transceiver or receiver of such a node running program 1200is put in a receive mode or turned on.

At step 1208, a check is made to determine whether an incoming signal isdetected with sufficient strength by such a node's transceiver orreceiver. A receive signal strength indicator (RSSI) may be used fordetecting a signal of sufficient strength. If signal is detected at step1208, then at step 1209 a determination is made as to whether a messageassociated with such detected signal is correct. In other words, hasthis received information been corrupted.

Well-known forward error correction algorithms, including but notlimited to Convolutional Coding, Block Coding and the like, may be usedfor determining whether information is corrupt. Interference is a reasoninformation may be corrupted; however, there are many other well-knownpossible reasons. If such information is not corrupted, then theincoming data is processed at step 1221. Such slot remains in use, andsuch a node executes instructions to check for a next slot in this frameat step 1206.

If such information is corrupted, then error information is stored atstep 1211. At step 1210 a check is made to determine if failure rate forrepeated use of such a selected slot is too high. An acceptable failurerate may be in a range of approximately one percent (1%) to five percent(5%) of packets depending on application. If failure rate is not toohigh, then such slot remains in use. A check is then made for anotherslot at step 1206. Recorded errors may be stored in a database in memory307 of node 300 of FIG. 3. During a later frame, this recorded error mayprovide an indication that an accumulated error rate for such a timeslot has become too high.

If, however, such failure rate is too high, then at step 1212 usage ofthis slot is canceled. At step 1213, this cancellation is advertised toneighboring nodes to such a node running program 1200.

At step 1214, detected interference is characterized, such as by time,frequency, power, and probable transmitter location. Accordingly,information from step 1214 may be stored, for example in memory 307 ofFIG. 3, for subsequent access for later slot allocation attempts.

If no signal is detected or a signal of insufficient strength such thatno data is obtained at step 1208, then at step 1220 such errorinformation is stored. At step 1215 a check is made to determine iffailure rate, as described above, for such a node is too high, asdescribed above. By way of example and not limitation, signal may not bedetected if a transmitter of a transmitting node is not working or notworking properly. If such a node's receiver is not working properly orif the slot allocation assertion messages previously described were notexchanged properly. If failure rate is not too high, then suchcommunication slot remains in use. At step 1206 a check for anothercommunication slot within a frame is made.

If, however, failure rate is too high, then at step 1216 a check is madeto determine whether a plurality of receive slots from the sametransmitter are failing. This indicates whether a transmitting node isunaware of such a specific slot allocation, or is malfunctioning, or isbeing blocked, such as by an obstruction between transmitting andreceiving nodes. If not all receive slots are failing, then at step 1217neighboring nodes to such a node are re-informed of planned slot usagefor such a communication slot. Accordingly, such a communication slotremains in use and a check for another communication slot is made atstep 1206.

If, however, at step 1216 approximately all communication slots arefailing, then at step 1218 all communication slot assignments to thisreceiving node from an associated sending node are canceled.

At step 1219, nodes neighboring such a receiving node, are informed ofsuch a cancellation of all communication slot assignments associatedwith such a sending node, and a check for a next slot is made at step1206.

Network Join

Referring to FIG. 13, there is shown a flow diagram of an exemplarynetwork join protocol 1300 in accordance with an aspect of the presentinvention. Program or protocol 1300 is used for an isolated node 101 or102 to join network 100 or for two networks to join. By isolated node,it is meant a node 101 or 102 not yet having joined network 100 or anode 101 or 102 having lost contact with network 100. For example, a newnode communicates its presence and waits to be contacted by a node onnetwork 100 of FIG. 3 or vice versa. With this contact, such a new nodemay receive current operating parameters. The overreaching concept is toachieve at least one link to another node and then use that link toobtain data from a shared database. This data provides in partcommunication information for nodes within a neighborhood. Once suchdata is obtained, network connectivity may be enhanced.

One or more communication slots designated for use by a network joinprotocol are known as “hello” slots. Unlike other communication slots,use of “hello” communication slots is not allocated and asserted priorto usage, but rather is contention based. Allocation of additional slotsspeeds operation of such a network join protocol. However, one “hello”slot per frame is sufficient.

At step 1301, program 1300 waits for a next “hello” slot, moreparticularly, a midpoint between two next “hello” slots. When such anext “hello” slot is available, at step 1302, it is determined whethertransmit, or receive, occurred on a previous “hello” slot.

If transmit occurred on a previous “hello” slot, antenna and frequencyused for such a previous “hello” slot transmission are obtained at step1325. At step 1326, a receive is scheduled in a next network join or“hello” communication slot using frequency and antenna obtained at step1325. Then, at step 1301, program 1300 waits for another “hello” slot.

If, at step 1302, it is determined that a previous “hello” operation wasa receive function, then at step 1303 it is determined whether a messagewas received on such a previous frame. If no message was received onsuch a previous frame, then at step 1310 a frequency is randomlyselected. At step 1311, an antenna is randomly selected using weights.By weights, it is meant using knowledge from prior experience. Forexample, a weighting for each antenna or sector, W_(s), may be set equalto,W _(s)=(1+number of known nodes within a sector)/(Σ_(i) W _(s) _(i)).  (4)

At step 1312, a transmit probability is computed as a function of such anode's network status. Such a transmit function should provide a highprobability of transmission (approximately 0.9) for an isolated node, amedium probability of transmission (approximately 0.5) for a node with afew links to other nodes, and a low probability (approximately 0.1) fora node with many links to other nodes and in particular for a node withbackhaul connectivity.

At step 1316, a number is randomly selected from 0.0 to 1.0. At step1317, it is determined whether the number selected in step 1316 isgreater than probability set at step 1312. If such a number from step1317 is greater than such a probability from step 1312, then at step1326 a receive operation is scheduled as described above. If such anumber from step 1317 is less than or equal to such a probability, thenat step 1318 a message called a “hello” request is formed and queued.Form of such a “hello” request comprises a header including messagetype, node identification and time. Such “hello” messages may alsocomprise a number of records from a shared database, for example, nodelocation record and node status record. This additional information isused to update or populate a local database of such a node runningprogram 1300.

At step 1319, transmit power is selected as a function of nodes in aselected antenna sector of step 1311 and time since a last link with anynode in that sector. A goal is to use a minimum transmit power needed toreach another node. If however a search has been conducted for some timewithout success, than transmit power is increased to expand the scope orrange of transmission of a “hello” request.

At step 1320, a transmit operation is scheduled for a next “hello” slotusing frequency from step 1310, antenna from step 1311 and power fromstep 1319. Then, at step 1301, program 1300 waits for another next“hello” slot.

If at step 1303 a message was received on a previous “hello” slot, thenat step 1304 a node sending such a message is entered into a database,namely, a shared database of other nodes as mentioned above. At step1305, other records contained in such a message may be entered into theabove-mentioned database.

At step 1306, it is determined whether a message from step 1303 is a“hello” response or a “hello” request. If at step 1306 it is determinedthat such a message type is a request, namely not a response, then atstep 1321 it is determined whether there is an existing route to such anode sending such a request. If there is a known or existing route,program 1300 proceeds at step 1310 as previously described. If there isno existing route, then at step 1322 a communication slot is made forthis node running program 1300 to receive data from a responding node.Making this slot involves checking for conflicts and interference aspreviously described. At step 1323 a “hello” response is formed andqueued. Form of a “hello” response at step 1323 comprises node location,node status, current frame plan and slot assignment records.

At step 1324, transmit power is selected, as previously described, toreach such a node sending such a request. Then, program 1300 proceeds atstep 1320 as previously described.

If at step 1306 it is determined that such a message is a “hello”response, then at step 1307 it is determined whether such a messagecontains at least one communication slot assignment for this node 101 or102 running program 1300. A “hello” response is provided in reply to a“hello” request, and thus a “hello” response states where it is and howto communicate with it. If there is no communication slot assignment,then program 1300 proceeds to step 1310 described above.

If there is at least one communication slot assignment, then program1300 proceeds to step 1308 to cancel any and all existing receive slotsfrom this sending node. This action is taken because the other noderesponds only if it does not have knowledge of any route between the twonodes. At step 1309, a receive slot is made for this node runningprogram 1300 to receive data from such a responding node. Making thisslot involves checking for conflicts and interference as previouslydescribed. Then, program 1300 proceeds at step 1310 as previouslydescribed.

Actual sending of scheduled messages with respect to steps 1320 and 1326is done within a frame execution program, as described above. Notably,though a response is described above as providing information forcommunication to such a responding node, such a response may compriseinformation for communication in both directions, namely to and from arequesting node.

Although the network join protocol as described allows a new node tojoin an existing network without the provision of any configurationinformation, providing such information can significantly speed suchnetwork join protocol. Additional configuration information may beprovided in many ways, including: providing a new node with a list ofone or more existing nodes and their locations, or providing existingnodes with the probable location of a new node. Such information can beprovided to nodes either manually, downloaded over a communication link,loaded through a media interface, or gleaned by passively monitoring aradio channel of interest for sources of energy.

Accordingly, it should be understood that a node selects how to allocatechannels for network traffic, in part determining bandwidth availabilityand dynamically allocating bandwidth for transmission of such traffic.Nodes may communicate with one another by point-to-point, broadcast, ormulticast communication, though some nodes are neither an originatingnode or an ultimate destination node for a message. Such a mesh protocolin accordance with an aspect of the present invention facilitatesextended communication range and continued service by distributedchannel management for dynamically allocating around conflicts andinterference.

Each node's configuration within a network is determined at least inpart by neighboring nodes in such a network. Thus, it should beappreciated that a mesh protocol in accordance with an aspect of thepresent invention reduces costs associated with deployment by reducingthe amount of infrastructure required. Additionally, use of neighboringnodes as infrastructure reduces the requirement for extendedcommunication range, simplifying customer installation complexity.Neighboring nodes do not serve as such infrastructure in other wirelessarchitectures. Moreover, each node may make channel allocation decisionsfacilitating scaling of such a network.

Furthermore, a network in accordance with an aspect of the presentinvention provides users significant bandwidth. By way of example, ifeach node is capable of communicating at approximately 36 megabits persecond (Mbps) and for every 100 nodes in a mesh, and if each time slotcan be reused by eight transmitter/receiver pairs, then such a networkis capable of transporting 288 (36 Mbps*8) Mbps. Thus, for example, ifeach packet is forwarded through two intermediate nodes in such anetwork, each packet is transported three times, namely, three hops, sothat 96 Mbps of non-duplicated information may be transported at anyinstant in time in such a mesh. If one-half of such nodes are being usedby customers and are actively transmitting or receiving customertraffic, not intermediated nodes, each customer is capable of achievingan average of 1.92 (96 Mbps/50) Mbps of bandwidth using a singlefrequency channel. Notably, this may be asymmetric or symmetriccommunication.

An aspect of the present invention is a mesh architecture, or moreparticularly a synchronous mesh architecture, that may comprise onlypoint-to-point links, only point-to-multipoint links, only broadcastlinks, or any combination thereof. Currently, in the United States ofAmerica transmit power on UNII band broadcast or point to multipointlinks is limited by the Federal Communications Commission (FCC) to fourwatts Effective Isotropic Radiated Power (4 W EIRP) while point-to-pointlinks are limited to two hundred watts EIRP (200 W EIRP). Thus, anetwork formed of only point-to-point links may benefit from a decisiverange and link closure advantage.

Aspects of the present invention comprise programs, which may beimplemented as a program product for use with a node 300, for example,by programming memory 307 of FIG. 3. Alternatively, such programs may beprovided to a computer. The program(s) of the program product definesfunctions of the embodiments and can be contained on a variety ofcomputer-readable media, which include, but are not limited to: (i)information permanently stored on “non-writable” storage media (e.g.,read-only memory devices within a computer such as CD-ROM disks readableby a CD-ROM drive); (ii) alterable information stored on “writable”storage media (e.g., floppy disks within a diskette drive or hard-diskdrive); (iii) information stored on integrated circuit memory. Suchsignal-bearing or computer-readable media, when carryingcomputer-readable instructions that direct the functions of the presentinvention, represent embodiments of the present invention.

Although various embodiments which incorporate the teachings of thepresent invention have been shown and described in detail herein, thoseskilled in the art can readily devise many other varied embodiments thatstill incorporate these teachings.

All trademarks are the property of their respective owners.

1. A method for slot allocation acknowledgement by a node, comprising:providing slot allocation information; determining if the slotallocation information has been superseded; if the slot allocationinformation has not been superseded, determining whether the slotallocation information pertains to the node; if the slot allocationinformation pertains to the node, determining a mode associated with theslot allocation information; if the mode condition is transmit orreceive, checking for conflicts and interference with the slotallocation information; if the slot allocation information is notconflicted and not precluded by interference, scheduling use of acommunication slot identified by the slot allocation information;determining whether the mode condition of the slot allocationinformation involves activity within an interference area of the node;and if the activity is within the interference area, advertising theslot allocation information to neighboring nodes of the node.
 2. Themethod of claim 1 further comprising if the mode condition is none,unscheduling usage identified by the slot allocation information.
 3. Themethod of claim 1 wherein the advertising is only by point-to-pointcommunication.
 4. The method of claim 1 wherein the advertising is onlyby point-to-multipoint communication.
 5. The method of claim 1 whereinthe advertising is only by broadcast communication.
 6. The method ofclaim 1 wherein the advertising is by one or more of point-to-pointcommunication, point-to-multipoint communication and broadcastcommunication.
 7. The method of claim 1 further comprising if the slotallocation information is not conflicted and not precluded byinterference and if the mode condition is a receive mode, acknowledginga sender of usage identified by the slot allocation information.
 8. Themethod of claim 7 wherein the acknowledging is only by point-to-pointcommunication.
 9. The method of claim 7 wherein the acknowledging isonly by point-to-multipoint communication.
 10. The method of claim 7wherein the acknowledging is only by broadcast communication.
 11. Themethod of claim 7 wherein the acknowledging is by one or more ofpoint-to-point communication, point-to-multipoint communication andbroadcast communication.
 12. The method of claim 1 further comprising:if the slot allocation information is conflicted or precluded byinterference, canceling a slot allocation identified by the slotallocation information; and advertising the neighboring nodes of thenode of the canceling of the slot allocation.
 13. The method of claim 12wherein the advertising is only by point-to-point communication.
 14. Themethod of claim 12 wherein the advertising is only bypoint-to-multipoint communication.
 15. The method of claim 12 whereinthe advertising is only by broadcast communication.
 16. The method ofclaim 12 wherein the advertising is by one or more of point-to-pointcommunication, point-to-multipoint communication and broadcastcommunication.
 17. A computer-readable medium containing a programwhich, when executed by a processor in response to receiving slotallocation information, causes execution of a method comprising:determining if the slot allocation information has been superseded; ifthe slot allocation information has not been superseded, determiningwhether the slot allocation information pertains to the node; if theslot allocation information pertains to the node, determining a modeassociated with the slot allocation information; if the mode conditionis transmit or receive, checking for conflicts and interference with theslot allocation information; if the slot allocation information is notconflicted and not precluded by interference, scheduling use of acommunication slot identified by the slot allocation information;determining whether the mode condition of the slot allocationinformation involves activity within an interference area of the node;and if the activity is within the interference area, advertising theslot allocation information to neighboring nodes of the node.